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By Lars Clausen, Denmark since 2006.
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D-Clock Audio Reference Clock

High End Audio Reference Clocks for upgrading of CD players, DVD players, SACD players, Computer Soundcards, etc.

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Customer Feedback:
Hi Lars

It is now connected and fully working. This is the best upgrade I have done!!! Fantastic!

Best regards

Customer Feedback:

I promised I would return some feedback after installing the D-Clock in my Yamaha CDX-993 (Yamahas flagship ten years ago, a good machine that I have tweaked earlier with AD826 op-amps). After running it in, the result is beyond expectation, regardless if I listen to classical music or rock. I did not realise that there were so much musical information hidden in my CDs. More detail and clarity, the previously deep and firm base is even deeper and firmer, treble is very clear and distinct but not intrusive. The channel separation has improved and there is a much better sense of room and positioning of the instruments. Piano, accordion and cymbals sounds notably better than before. The negative part of it is that some records that previously sounded OK now are less enjoyable, when bad recording technique shines through.

Alltogether, I am very content with purchasing the D-Clock.
Best wishes

Lars, Stockholm, Sweden

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Frequencies of:
6.000000 MHz
8.467200 MHz
11.289600 MHz
12.000000 MHz
12.288000 MHz
16.934400 MHz
22.579200 MHz
24.576000 MHz
27.000000 MHz
28.322000 MHz
33.868800 MHz
45.158400 MHz

Accuracy: +/- 1ppm
Jitter: 1.5pS
Df(9-24V): Max 1Hz
Control Functions: Host Vcc
Power Supply Requirements: 9.00 - 24.00 Volts DC 20 mA

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Noise and Jitter Free Clock Signal.
Due to the special output configuration, the clock signal is absolutely noise and jitter free, and that is the most important feature of a reference clock. [Here seen in the 3V mode]. In terms of sound quality you get a rock solid sound stage, with a wide, deep and natural placement of the performers. That is nothing new, when using an audio clock. But how many times have you heard about people spending vast amouts of money optimizing the power supply of their clocks? Well with the D-Clock it's no longer necessary.

The reason for using an external power supply is not a matter of getting more power, or even noise free power. Every audio clock has it's own low noise power regulator to eliminate voltage drop and high frequency noise. And when you add a new mains transformer to your supply, you actually get a lot of new capacitively coupled noise into your audio clock power supply. Still the addition of a high quality power supply is a significant improvement. That is because the external power supply is the only way you can eliminate ground loops from the CD player's power supply to the sensitive digital/analog converters. Or was!

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Isolated Clock Injection Point.
As a unique feature, the clock signal is isolated from the power supply GND, so you get no GND loop, and also you get no Mains Noise injection.
This is achieved with a 100 MHz micro pulse transformer, with an isolation capability of 1500V. The Power GND and the sensitive Digital GND can no longer see each other, and so you get a cleaner clock signal.
Not only does the isolator remove any power supply noise, and GND loop, it also makes the connection to the CD / DVD player much simpler. Remove the Crystal, and two capacitors, form the CD player, and connect the cable.
The capacitor in series with the clock signal is a special PET type with good sound qualities.

Please Note, the blue LED is used for indication only.

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When we say 'Micro' ..... .
The clock isolation transformer consists of two microscopic toroid transformers, (around 3 mm diameter). One is used for the isolation function, the other is a common mode choke, that prevents noise spikes from the outside, entering the reference clock backwards. This particular isolator transformer is designed for high speed pulse communication, such as found in local area networks. (Up to 100 MHz). The whole package shown here is just 12.7 mm (0.5') wide.

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Ultra Low Noise Power Regulation.
The Power Supply Regulation for any reference clock is critical. We use a double pre regulated version with a central reference type LM329DZ. This reference has the lowest inherent noise, and thus needs less post filtering than most other regulators. The internal clock circuit core runs on it's own separate supply, and output stage can be run on either 3 or 5 V to connect to various players. DVD players usually take 3V mode, while CD players usually uses 5V. You can experiment for the best result.
Power Connection to the outside world is achieved with a 'Micromatch' connector, with cable 30 cm included. Directly after that a set of GND and Power filtering chokes with special Q dampers. These remove noise above 2 MHz, also from the GND of the power supply. This is only possible because of the special output isolation, and makes the D-Clock simulate battery operation.

A pair of power holding capacitor with totally 1100uF is used to stabilize the power supply for the D-Clock. This is smaller than found on some other clocks. The D-Clock however has around 4 times lower power consumption and so a large capacitor is not needed to hold the supply up the same amount of time. And more importantly a smaller Low-Z capacitor has much better high frequency filtering capability than a large can.

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Protective Ground Plane.
The inside of a CD or DVD player is a very noisy environment, as thousands of small digital circuits inside the LSI chips generate electromagnetic noise. That is why you should use a solid ground plane to act as a shield against these noises, and prevent them from degrading the performance of your reference clock. Normally this is solved in high-end clocks by using 4 layer PCB with internal GND plane.

However we have found that the minute capacitances from the pads to the GND plane, with only a very thin layer of epoxy resin as a isolator, is enough to affect the performance and temperature stability of the clock. The epoxy resin is not a very temperature stable dielectric material.
One solution is to use Teflon based PCB, but that is both very expensive and also tends to give the sound a bit of excessive dryness.
Our solution is to reduce to 2 copper layers, but use the whole 'bottom layer' as a GND plane. This takes a lot of maticulous planning on the layout part, you have to keep all the signal tracks on the top layer, but pays itself in 4 times lower stray capacitance.
As you can see the GND plane near the output plug belongs to the CD player's sensitive digital GND, and is isolated from the rest of the D-Clock GND plane.

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You can disable the clock output with a voltage signal. This is useful if you have a constant power source for your clock (like an external PSU or in a DVD where the power is controlled by a microprocessor, so your Clock power is on, while other circuits are turned off). If you use a simpler clock in this case, your CD or DVD player can be damaged.
In the D-Clock we have provided an effective solution. The VCC of the host player can be connected to the 'Host VCC' pad, and the Host VCC detector activated. When the D-Clock detects voltage 3.3 or 5V on this pad, the clock signal is admitted. When power is off, the clock signal is stopped to prevent latch-up of the input circuit of the player.
In most normal cases however, the clock power is turned on and off with the host player, so you can 'Ignore' (Default) the host VCC. This is done by leaving the 'Ignore' pad shorted with solder. In other words you don't have to do anything. If you want to use the Host VCC detector, you must remove the solder from the 'Ignore' pad.

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Power Supply for the D-Clock can be derived from the CD or DVD player very easily. Use a Voltmeter to establish the voltage across the power supply capacitors (start with the biggest cans in the player). Since the output is isolated, you don't have to worry about whether the particular part of the PSU is connected to the digital processors or not. This makes successful installation of D-Clock much simpler than most clocks.
If the voltage is steady when the player is on, and in the range of 9 - 25 V DC, then you can use this power source. The red or blue wire of the power cord is GND, while the grey one in the other side of the ribbon cabe is +. The two first, and two last wires are connected with each other in the connector.

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Some CD or DVD players run with 5V supply, others with 3.3V. Most low cost clocks only give you one option, and that is 5V. If you connect a 5V clock to a 3.3V CD or DVD player, you may very well damage the sensitive circuits. That is why we provide you with a voltage setting on D-Clock. This allows you to adapt the output closk signal to fit your player perfectly. Use a simple Voltmeter to determine whether your player uses 3.3V or 5V power supply. You can find the voltage on the small brown components sorrounding the chip, where the original crystal of your player is connected. By default the D-Clock is set to 3.3V (3.3Vpp clock signal). If you want to set it to 5V, simply add solder to the '5V' bubble. (5Vpp clock signal).

Power Supply Cable and Clock Signal Injection Cable are included with every D-Clock.

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Interface to a DIP 8 oscillator footprint.

Many CD players are equipped with a DIP8 crystal oscillator like this one:

Remove the crystal oscillator from the main board, and connect the D-Clock cable as seen here:

The diode is optional, you only have to mount it in case the clock signal is not received properly by the host machine (if you hear dropouts). Use 1N4148, 1N914 or similar.

NewClassD ApS | DK7500 Holstebro | Denmark | tel +45 32130963 | E-Mail: |26172